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Vuichard technique for settling with power?

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Vuichard technique for settling with power?

Old 15th Mar 2015, 12:36
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Torquetalk,

Given the mis-understanding between VRS/SWP/Power Settling, etc. I'd say it isn't being taught correctly many places. It was discussed, I'd say more time was spent on tail rotor effectiveness. But the rate of descent needed to teach that in a UH-1 is pretty silly when the other hand is telling the student not to exceed 800fpm (can't remember if we used the 500fpm ROT back then) on the approach.

I don't see why it couldn't be put into a SIM, the old Huey sim at Rucker would simulate a loss of tail rotor gearbox. That was a rough ride.

I think crab said it better. I'll admit having the lightest helo a pilot has ever flown be a UH-1 isn't the norm around the world either.
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Old 15th Mar 2015, 16:52
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I still teach incipient vrs and in particular the areas where it is most likely to happen i.e. downwind landings and low and slow aerial photography going round and round a target
It is absolutely essential that it is taught. I show students that in a 300 and 500 that the machines vibrate when losing translational lift I remind a student to check their vertical speed as the onset of this rumble if more than 500ft a min think about going round ! One can have a 500ft vertical descent in either machine with less than 20 its and pull collective and it will climb. Get that to 700 to 800 ft and I start breaking into a sweat and have my body weight poised over the collective ( i am 100kgs ) in case the lever is unexpectedly pulled up !
People are right the standard of training is woeful everyone seems to concentrate on pointless exercises such as Vor tracking for instance and not on the more important things !
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Old 15th Mar 2015, 17:53
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Hughes500, All of that sounds perfectly reasonable and isn't any different really than the way I was taught. But do you take your student out intentionally setup in your case an 800fpm descent below ETL and then add collective? I guess that's what I envisioned when guys said they "taught" VRS.
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Old 15th Mar 2015, 19:43
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TC

The RN was still teaching your list of fun stuff when I went through in the 90s, plus annual VRS reminder in the Seaking. I fondly remember the out of control falling sensation....


That all said, can any of the wise heads here tell me why fully lowering the lever doesn't instantly take you out of VRS?
You should be clear of the vortex almost instantly, surely?

Just to be clear, I know it doesn't work quite like that, I just want to know why.
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Old 15th Mar 2015, 19:48
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Busdriver

I certainly do but putting into incipient vrs is fine, I describe it to the student as the helicopter not wanting to fly ( the whole airframe is shuddering through the base of your seat as opposed to vibrating through the controls ) at this point stick the cylic forward, as soon as the ac stops shuddering apply full power and maintain fwd cyclic to climb away( as the nose will violent rise with full power ). I am trying to teach " muscle memory " I know you might not require full power but prefer to teach that and then slacken power rather than the other way. Bear in mind the average private guy takes no or little continuation training so really have to drum it in !
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Old 15th Mar 2015, 22:12
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Back to the original topic of the thread: the whole point of the "Vuichard" recovery technique is to get out of a vortex in situations where you don't have sufficient altitude for a standard recovery (i.e. lower collective and pick up speed before you raise collective again). This can be applicable e.g. when long lining and in this situation you should have HOGE power (i.e. you're not settling because you have insufficient power).
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Old 15th Mar 2015, 22:25
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That all said, can any of the wise heads here tell me why fully lowering the lever doesn't instantly take you out of VRS?
You should be clear of the vortex almost instantly, surely?

Just to be clear, I know it doesn't work quite like that, I just want to know why.
Not a wise head by any stretch, but here is what I think.
Yes, fully lowering the lever will instantly get you out of VRS (and into an auto), but your ROD and inertia at that point can be quite significant, to the tune of thousands of fpm in the extreme.
So even if forward speed is quickly gained at that point, you'd still need to arrest the high ROD, and near the ground, where inadvertent VRS is most likely, there is not a lot of cushion for that. Even if normal auto ROD is less than 2000 fpm, the VRS ROD can be much greater, and being in auto doesn't instantly reduce the ROD.
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Old 15th Mar 2015, 22:43
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Fair enough, I suppose my frame of reference is stuck in a helicopter that would require something like 1500fpm to get into that regime.

On topic, is this technique based on shortest distance to get out of the vortices? Why would this take less altitude than nosing over? I suspect most folks aren't comfortable putting the nose down 20 degrees, but are perfectly happy with 20 degrees of bank.
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Old 16th Mar 2015, 07:40
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Jymil, you're absolutely correct. I learned this recovery technique a long time ago while flying a longline. After a bit of practice, the recovery maneuver can be done quickly and without much drama.
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Old 16th Mar 2015, 08:02
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busdriver - I think the point of this technique is that in full VRS, cyclic response can be erratic and sluggish, whereas the TR should be clear of any vortex.
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Old 16th Mar 2015, 11:52
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Crab: Morning to you, hope you're enjoying your new job!
I'm moving on also......still aviation.

WRT your last comments: don't forget - in FDVRS the tail rotor could and can get caught up in dirty air from the main rotor. ALSO as and when Nr decays during VRS, this drags the TRE by a disproportionate amount thus reducing its effectiveness even more.
Do not rely on the TR helping anyone out during VRS

This so called " Vuichard Recovery Technique" seems only to be relevant to recovery during Settling with power and not FDVRS, I would suggest...............

The last thing one would want to do during VRS is to pull FULL collective power
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Old 16th Mar 2015, 14:43
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Are there any references to the Vuichard technique in particular how\why it is suppose to work?

The only reference I could find googling is the wikipedia article (or direct quotations from it), and let's face it neither wikipedia (nor anonymous forum posts!) are necessarily reliable sources of information.

The wikipedia article suggests the technique is described in the 2013 R22\R44 Flight Training Guide (which looks like it is only available in hard copy from Robinson).

Matthew
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Old 16th Mar 2015, 16:10
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TC - congrats on the new job - do pm me with details.

Very happy in my new role

I think this technique is only suitable for VRS, definitely not for SWP as you are already decaying the Nr as you overpitch which, as you say, degrades TR thrust markedly.

I know yaw variations can be a theme of VRS due to the 'bursting bubble' disruptions from the MR upwash and, in this case, the TR would be less effective.

However, not every episode of VRS will give those symptoms and it will vary with aircraft type. Equally not every excursion into FDVRS will give Nr decay - that will only happen if you keep pulling until you hit engine limits.

It may be that this technique has some validity in some circumstances and it certainly can't make things worse if you are limited on recovery height available.
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Old 16th Mar 2015, 17:13
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Are there any references to the Vuichard technique in particular how\why it is suppose to work?

The only reference I could find googling is the wikipedia article

The wikipedia article suggests the technique is described in the 2013 R22\R44 Flight Training Guide (which looks like it is only available in hard copy from Robinson).
One question I CAN answer since I started the thread... the only place I've seen is the Wiki article and some things that quote it. It came up because the friend who was with me when it happened - who is also a fixed wing & autogyro pilot and very curious about things in general - looked around and I guess found the Wiki article.

It certainly isn't described in the R44 POH, which I have at home.
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Old 16th Mar 2015, 21:13
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"WRT your last comments: don't forget - in FDVRS the tail rotor could and can get caught up in dirty air from the main rotor. ALSO as and when Nr decays during VRS, this drags the TRE by a disproportionate amount thus reducing its effectiveness even more.
Do not rely on the TR helping anyone out during VRS

This so called " Vuichard Recovery Technique" seems only to be relevant to recovery during Settling with power and not FDVRS, I would suggest...............

The last thing one would want to do during VRS is to pull FULL collective power."

Interesting thoughts, TC. If the tail rotor thrust and anti-torque were compromised then I think the expected torque effect yaw would present. If not, I would expect that the TR was still effective and might be helpful in slipping the aircraft into 'clean air' without the considerable loss of altitude with the conventional recovery. I do wonder what advantage the described technique offers to just putting the nose down.
I share your apprehension at increasing power in VRS situation.
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Old 16th Mar 2015, 22:22
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A couple of thoughts on this from a 200 hr pilot, (but an engineer).
When full lever down, lift is still created by the rotor. As proved in my R44 with a solo auto, cold day, little fuel, full down lever still doesn't drive rpms into green, and the whole auto can be performed with the lever down.


Therefore, lift is still being created at full lever down, therefore downwash is still being created, therefore downwash is still being added to the VR column even as we pray for the machine to drop through that column.


When the cyclic is rammed forward and not much happens, it is because we're still roughly at the speed of the downwash, so not much of a horizontal vector is created because not much "felt" by the rotor disk.
s
So, fully developed VRS, drop the lever, ram the cyclic forward, you have to wait for the machine to drop THROUGH the downward column of air, which it is still adding to somewhat, or hope what little horizontal vector you can put on the disk will pull the machine forward out of the column.


On the other hand, if the tail rotor is outside the column of air going down, it can add significant translational force to the right ('Murican helis), while crossing the controls adds to that translation to the right with whatever horizontal vector the rotor disk can bite out of the downward column. Sidestep 40 feet to the right, and viola! Clean air. So, in theory, that seems to me the underlying cause that the vuichard technique might be quicker.


Or not. I'm just a rookie.
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Old 16th Mar 2015, 22:41
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Why I went the way I did:

Tail rotor effectiveness or not, unless I'm missing something accelerating the airflow over the disc is key. Just booting the tail out wouldn't cause an acceleration. Given it's supposed reference in the R22 manual (wiki source, I have no truth data) it seems more a link to getting the disc tilted rapidly without getting negative G and the associated mast bumping problem. If I were concerned with mast bumping and felt the onset of VRS, I could make a faster recovery with this technique just based on time to get to say 20 degrees of tilt. I guess I fail to see what cross controlling does different than shoving the nose into the dirt. Both rely on having some level of cyclic control remaining, just a different axis.

Not trying to be a snarky smart ass, I swear.
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Old 16th Mar 2015, 23:18
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Well, I think that is why you apply full right cyclic with power pedal. If it was just power pedal you'd get mainly yaw. But with power pedal and cyclic you get translation. If the cyclic is full forward, or full right, you get the same horizontal vector. In fully developed VRS, not much. But, add in the full power pedal and you get the sum of the two horizontal vectors, and by pulling full power you lessen the tendency to yaw as you boot in full pedal so the tail rotor is fighting the engine and all that hp is pushing everything to the right.
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Old 16th Mar 2015, 23:52
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Any way you cut it, I think accelerating at 1G in a helo is the realm of gravity only. I seriously doubt tail rotor thrust will make a significant impact. I have some experience trying to teach high angle strafe to AF guys/gals. They almost universally are not comfortable putting the nose 20-30 degrees down at first. All of them are perfectly fine banking the same number of degrees.
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Old 17th Mar 2015, 00:26
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Get into OGE. Go full up on collective, full left pedal. Don't move the cyclic. How long does it take you to move 40 feet off center? In theory, that's the incremental movement of machine vs column you get from vuichard vs just shoving the cyclic forward.


ummmm. You first.


Like I said, I'm just a rookie. And, I can only afford to fly the much maligned Robbies.


But, for what it's worth, when I got my ticket 2 years ago my instructor did spend time with me in FDVRS. I'm not afraid to shove the cyclic as far forwards as it would go, and I did, and nothing happened for what seemed like forever. We just kept going down. And this VRS demo, which he has repeated with me a couple of times since as I do reccurency, is the only time he's up on the edge of his seat, hand hovering over the lever, looking pretty worried.


I won't be testing my understanding of this theory, or betting anything on it, in the future. But, it's a good thing to have in the back of my head if I'm stupid and inattentive enough to get past incipient VRS, can't get out of it, and have nothing left to try. And I never intend or have to do that because I'm not only a rookie, I'm an amateur. Peace out.
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